TokenFactorySolution.sol

import "browser/My1stToken.sol";

pragma solidity ^0.4.16;

contract TokenFactorySolution {

    mapping(address => address[]) public created;
    mapping(address => bool) public isMy1stToken; //verify that given address is of this token type

    function createToken(uint256 _initialAmount, string _name, uint8 _decimals, string _symbol) returns (address) {
        My1stToken newToken = (new My1stToken(_initialAmount, _name, _decimals, _symbol));
        created[msg.sender].push(address(newToken));
        isMy1stToken[address(newToken)] = true;
        newToken.transfer(msg.sender, _initialAmount); //the factory will own the created tokens. You must transfer them.
        return address(newToken);
    }
}